Radiation-sensitive control for the concentration of a chemical

ABSTRACT

This invention is a control for the supply of chlorine in a swimming pool. The water in the pool is continuously recirculated and filtered and a sample is taken from the recirculating water in regular sampling cycles and the metered sample has injected into it a metered amount of chlorine indicator. An optical method is used to measure the effect of the indicator and to control accordingly an injector for chlorine into the pool.

United States Patent Harper et al. 5] Feb. 15, 1972 [54]RADIATION-SENSITIVE CONTROL [561 References Cited FOR THE CONCENTRATIONOF A CHEMICAL UNITED STATES PATENTS 1 Inventors: Norman Craik p JohnHenry 3,466,450 9/ l969 Goodman ..250/2l8 2,254,782 9/194] Riche..250/2l8 Marshman; Henry Thomas Marshman, all

2,526,515 10/1950 Stern ..250/2l8 of Landfield House, Clarence Road, St.2 656 845 10/1953 dsa 250/218 Heine, Jersey Channel Islands, Great 1 yBmam Primary ExaminerWalter Stolwein [22] Filed: Feb. 10, 1969Allorneywatson, Cole, Grindle & Watson [21] Appl. No.: 797,801 ABSTRACTThis invention is a control for the supply of chlorine in a [30] ForelgnApphcauon Pnomy Dam swimming pool. The water in the pool is continuouslyrecircu Feb. 15, 1968 Great Britain ..7,537/68 lared and filtered and asample is taken from the recirculating water in regular sampling cyclesand the metered sample has Clm 350/218, 356/180 injected into it ametered amount of chlorine indicator. An op- [51 Cl. ..G0ln 21/26 fl h di d t a re the efiegt of the indicator and Field 0! Search 350/218;356/201, 205, 206, to control accordingly an injector for chlorine intothe pool.

9 Claims, 7 Drawing Figures PAri-imsnrea 15 Ian 3.643.102

SHEET 2 OF 4 INVENTORS Nocmrm Wu Mil Jam [NW l ama mm mwmuunm BY Ma&ZI/MJ%/% ATTORNEY PAIENTEBFEB 15 m2 3.643; 102

SHEET '4 OF 4 ATTORNEY RADIATION-SENSITIVE CONTROL FOR THE CONCENTRATIONOF A CHEMICAL concentration in repeated samples of the water, and acontrol for a disinfectant injector responsive to the measured level.The term injector is to be construed widely as including suchequivalents as a pump.

If the disinfectant concentration drops below a certain level 1 which isjust sufficient to kill all bacteria present, bathing can be dangerous,while if the level gets appreciably above this the disinfectant can bemost unpleasant particularly in the eyes of bathers. However, it isimportant that there should be a small quantity of free disinfectantabove the nominal sufficient concentration and that the disinfectantshall be reasonably well distributed. Methods of estimating how muchdisinfectant should be added by an attendant taking occasional sampleswith a test tube and adding a measure of disinfectant indicator arequite unreliable, partly because the sample may be taken at a point nearthe surface where the concentration will be low due to the action of thesun and not at greater depths where the concentration may be muchhigher. Also, adjusting for a low concentration by throwing in a bucketof disinfectant is very haphazard. The invention enables samples to betaken at regular intervals from a selected point, preferably a pointdownstream of a pump in a recirculating line for the water, where theconcentration is likely to be as low as at any other point in the pool.Also the invention enables disinfectant to be injected in a controlledmanner for example by continuously operating the injector which can bearranged to operate during one measuring cycle prior to the taking ofthe measurement in the next cycle. The control is therefore convenientlyan ON-OFF control in which disinfectant is added or not according as ameasurement of a sample shows that the disinfectant concentration is lowor not low.

One preferred method of measuring a sample is to inject a measuredquantity of disinfectant indicator into a measured quantity of waterconstituting the sample. Where the disinfectant is chlorine, theindicator may be one such as orthotolodyne which colors the water yellowwith an intensity depending on the amount of chlorine present. This canbe detected by shining light from a lamp through the water in thechamber on to a photoelectric cell, preferably a photovoltaic cell toobtain a high output signal which will be a measure of the amount ofchlorine present. The signal can then be compared with a referencesignal and be arranged to initiate operation of the injector or notdepending on whether it indicates that the chlorine concentration is lowor not. This method uses the indicator economically because a smallquantity of water can be used as the sample and the amount of indicatorinjected can be correspondingly low.

The invention may be carried into practice in various ways and twoembodiments will now be described by way of example with reference tothe accompanying drawings, in which:

FIG. I is a diagrammatic elevation of a swimming pool having a chlorinecontrol arrangement according to the invention;

FIG. 2 is an elevation showing the general arrangement of the chlorinesampling unit;

FIG. 3 is a plan view of a sampling unit;

FIG. 4 is a section on the line IV-IV in FIG. 3;

FIG. 5 is a section on the line V-V in FIG. 3;

FIG. 6 is a circuit diagram, and

FIGv 7 is a diagram of an alternative unit.

As shown in FIG. I a swimming pool 11 has a pump I2 for continuouslycirculating water from a drain 13 through a filter 14 and back into thepool inlet 15.

In order that the chlorine level can be determined a branch passage fromthe connection between the pump I2 and the inlet 15 as shown at 16enables part of the water to be drawn off to a sampling unit 17, andafter sampling, this drawn off water is allowed to run to waste. It willbe seen that the sample is taken from just downstream of the pump 12which is the point in the cycle where the chlorine level will be thelowest. A signal from the sampling unit 17 is fed to a control circuit18 which controls a servo-operated chlorine injector device 19 which caninject shots of chlorine either directly into the pool as shown at 21,or into the passage leading into the inlet 15 down stream of the sensingunit as shown at 22.

There is a known chlorine level of about 0.3 parts per million at whichbacterial action is just prevented and in general it is desirable thatthe chlorine level should be slightly above this level to allow somefree chlorine. However, it is important that the chlorine level shouldnot be too high so that it does not cause discomfort to bathers.

The sensing unit 17 is arranged to give an inject signal or notaccording as the chlorine level sensed is below or above 0.3 parts permillion.

The unit is arranged to operate in continually recurring l5- minutecycles, and if the chlorine level is detected (near the beginning of thecycle) to be less than 0.3 parts per million. the chlorine injector isswitched on and held on for the remainer of the 15-minute cycle. Whetheror not the injector will be switched on in the next cycle depends on thereading of the sampling unit when the next cycle commences.

The equipment is shown generally in FIG. 2. The sampling unit 17 (shownin detail in FIGS. 3, 4 and 5) is mounted in an assembly which alsoincludes an electrical supply and a transformer, a synchronous motordriving a cam shaft through a reduction gearbox at a speed of 4revolutions per hour to determine the 15-minute cycle, a tank 26containing a chlorine indicator liquid, orthotolodyne, and a printedcircuit board 27 carrying components of an electronic circuit 18. Theboard 27 can be removed for servicing and replaced. The whole of theequipment shown in FIG. 2 is included in a glass fiber reinforcedplastic case which also incorporates indicator switches and instruments.The cam shaft can be rotated by hand for maintenance.

The sampling unit shown in FIGS. 3, 4 and 5 comprises essentially aglass block 31 having a metering chamber 32 through which the water bledoff at 16 is passes through a ball valve 33, the sampling chamber 32exhausting to waste at 34. Water normally flows freely past the valve 33and through the metering chamber 32 to keep it flushed, but when a cycleis to commence one of the cams 25 closes the valve 33 to keep the waterstatic in the metering or viewing chamber 32, by means of a siliconrubber ball 35 being held down on its conical seat (FIG. 5).

The second cam then presses the plunger 37 of a chlorine indicatorinjector unit 30 so that a piston 39 supported on a p.t.f.e. diaphragm41 displaces the indicator in the piston chamber 42 and forces itthrough a nonretum valve 43 of the bicycle tire kind having a radialopening in a metal shaft 44, which opening is normally covered by arubber sleeve 45. The mechanical action of the cam is sufficient to openthis oneway valve 44-45. At the same time the indicator is preventedfrom flowing back to the tank 26 by a light nonretum valve 46. When thepiston 42rises again after the cam has operated the plunger 37, due tothe action of a spring 47, the light nonretum valve 46 can reopen topermit the chamber 42 to be recharged with indicator for a shot for thenext cycle. It will be appreciated that the piston chamber arrangementprovides a precisely metered amount of indicator to be injected into themetered amount of water in the viewing chamber 32.

As shown in FIG. 3, at opposite ends of the viewing chamber 32 arerespectively an electric lamp 49 and a photoelectric selenium cell, 51illuminated through a blue filter 52. The cell 51 is of the photovoltaictype giving an output voltage dependent on the amount of light fallingon the sensitive area. The amount of light reaching the cell 51 throughthe blue filter will depend upon the yellowness of the liquid in theviewing chamber and this will in turn depend on the amount of chlorinein the water, since the indicator injected into the viewing chambercauses a yellowing of the chlorine with an intensity increasing with theamount present.

The lamp 49 is switched on by a cam when the indicator has been injectedinto the viewing chamber and the lamp remains on for about 20 seconds toenable a steady reading to be obtained.

Finally at the end of the 15-minute cycle the first cam allows the valve33 to reopen so that water can again flow past the ball 35 to flush outthe viewing chamber 32 to waste, ready for the next cycle. The line fromthe pump 16 includes a restrictor 53 for preventing the pool from tryingto empty itself to waste through the line 16.

The circuit diagram is shown in FIG. 6 and it will be seen that themains supply 61 energizes the motor 24 and a neon indicator 62 and alsothe primary winding of the transformer 23. One secondary winding of thetransformer is a l-volt winding and is connected with the lamp 49through a switch 60 operated by the first cam 25.

A second secondary winding 64 provides the supply to the photocell 51.The photocell 51 is connected in series with a variable resistor 65, thetwo being in parallel with a potentiometer 66 connected across thephotocell supply. The variable resistor 65 and potentiometer 66 areadjusted so that the voltage between their wipers 67 and 68 will be zerofor a chlorine level of 0.3 parts per million.

These wipers are connected to the respective bases of transistors 71 and72 whose power supply is obtained conventionally from a fourth winding73 on the transformer 23 through a switch 70 operated by the second cam.The transistor 72 is normally biased ON while the transistor 71 isnormally biased OFF. As long as the voltages at 67 and 68 are equal orthe voltage at 67 is negative with respect to the voltage at 68, thetransistor 71 remains turned OFF, but as soon as the voltage at 68becomes negative with respect to the voltage at 67 in response to a fallof the chlorine level below 0.3 parts per million, the transistor 71 isturned ON and its output signal is amplified through an amplifier showngenerally at 73 to turn ON a silicon-controlled rectifier 74 connectedin series with the coil 75 of an operating relay. When the relay coil isso energized its contact 76 closes to connect the mains to the servounit for energizing the chlorine injector 19.

The transistor 71, its amplifier 73 and silicon-controlled rectifier 74are duplicated as shown generally at 77 in FIG. 6

to give additional reliability in operation.

It is to be noted that since the cell 51 is a photovoltaic cell, thevoltage change and resistance change in response to a change in thelight level falling upon it act together so that a signal of reasonablemagnitude can be obtained in response to a small change in brightness.

it is to be noted that the response of the system will depend upon theconditions. For example, if there is a high bathing load, an injectionof chlorine will be reflected more quickly in the sampling unit sincethe chlorine will be mixed more quickly. Again, the chlorine level willvary-at least near the surface-in response to the amount of sun fallingon the surface of the water. What is important is that there should befree chlorine above the nominal 0.3 parts per million, and this isassured by sampling at the point of lowest intensity of chlorine.

Reference has been made to concentration control in swimming pools, butclearly the invention is equally applicable to control of concentrationin other large masses ofliquid.

An alternative arrangement is shown in FIG. 7 in which similarcomponents have been given the same reference numerals as in the otherfigures.

in this case water flowing from the pump 12 to the inlet during regularrecirculation is tapped on when a solenoidoperated valve 81 ismomentarily operated to flush out and refill the glass tank 32 with themetered amount of water.

The chlorine indicator is injected into the tank 32 from the reservoir26 by means of a peristaltic pump 82 driven by a motor 83 when this isswitched on in a checking cycle. The metered amount of indicator is thusinjected into the tank 32 and because it is heavier than the water it ismixed by a mixing device consisting of a permanent magnet 84 extendingalong the bottom of the chamber 32 and vibrated by an electromagneticdevice 85 energized during the measuring cycle.

The cyclic operation of the solenoid valve 81, peristaltic pump 82 andthe electromagnet 85 are controlled by microswitches operated by camsgenerally shown at 86 driven by a motor 24 as described in relation tothe first embodiment. The water and indicator is eventually flushed outto waste when the next cycle commences.

The lamp and photocell arrangement is similar to that described in thefirst embodiment and they are positioned at opposite ends of the chamber32.

in other respects the operation is similar to the first embodiment. Thismodification has the advantage that each of the steps in the cycle iscontrolled by an electrical switch, operation of the switches beingcorrectly timed in relation to each other by a motor.

What we claim as our invention and desire to secure by Letters Patentis:

1. A control for the disinfectant concentration in a swimming pool,comprising; means for taking a sample of the water, a metering chamberfor receiving said sample, a peristaltic pump for injecting a meteredamount of indicator into the chamber, means within the chamber forstirring the contents of the chamber, electromagnetic means foroperating said means for stirring, means for determining the colorintensity of the sample and indicator after operation of said means forstirring, means for comparing a signal dependent on the color intensitywith a reference signal, means for controlling a chlorine injector independence on the comparison, a motor, and cam-operated switchescyclically controlled by the motor for controlling the timedrelationship between taking of the sample, injecting the indicator, andcontrolling the chlorine injector.

2. Apparatus for controlling the disinfectant infectant concentration inswimming pool water, comprising;

means for repetitively obtaining successive samples from a recirculatingline of said swimming pool,

means for receiving a measured amount of said sampled water,

first means for injecting a measured amount of disinfectant indicatorinto said means for receiving,

means for measuring the concentration of disinfectant in said measuredsample,

second means for injecting a measured shot of disinfectant into saidswimming pool water, and

means for controlling said second means to inject a measured shot ofdisinfectant into said pool if the measured concentration ofdisinfectant is below a threshold concentration, and not to inject ashot if the said measured concentration is above the thresholdconcentration, the means for obtaining samples being inactive to take asuccessive sample until adelay time has elapsed since disinfectant wasinjected into the pool.

3. Apparatus for controlling disinfectant concentration as set forth inclaim 2 wherein said second means for injecting includes a peristalticpump controlled by said means for measuring.

4. Apparatus for controlling disinfectant concentration as in claim 2wherein said means for repetitively obtaining samples receives saidsamples from a location wherein the disinfectant concentration is thelowest.

5. Apparatus for controlling disinfectant concentration as in claim 2wherein said means for repetitively obtaining samplings includes meansfor flushing said means for receiving prior to each successive sample.

8. Apparatus for controlling disinfectant concentration as set forth inclaim 2 further comprising means for discharging the measured amounts ofsampled water and indicator to waste and not to the pool after measuringthe disinfectant concentration.

9. Apparatus for controlling disinfectant concentration as set forth inclaim 2 wherein said receiving means includes a stirrer andelectromagnetic means for vibrating said stirrer to mix the water withthe indicator prior to measuring.

1. A control for the disinfectant concentration in a swimming pool,comprising; means for taking a sample of the water, a metering chamberfor receiving said sample, a peristaltic pump for injecting a meteredamount of indicator into the chamber, means within the chamber forstirring the contents of the chamber, electromagnetic means foroperating said means for stirring, means for determining the colorintensity of the sample and indicator after operation of said means forstirring, means for comparing a signal dependent on the color intensitywith a reference signal, means for controlling a chlorine injector independence on the comparison, a motor, and cam-operated sWitchescyclically controlled by the motor for controlling the timedrelationship between taking of the sample, injecting the indicator, andcontrolling the chlorine injector.
 2. Apparatus for controlling thedisinfectant infectant concentration in swimming pool water, comprising;means for repetitively obtaining successive samples from a recirculatingline of said swimming pool, means for receiving a measured amount ofsaid sampled water, first means for injecting a measured amount ofdisinfectant indicator into said means for receiving, means formeasuring the concentration of disinfectant in said measured sample,second means for injecting a measured shot of disinfectant into saidswimming pool water, and means for controlling said second means toinject a measured shot of disinfectant into said pool if the measuredconcentration of disinfectant is below a threshold concentration, andnot to inject a shot if the said measured concentration is above thethreshold concentration, the means for obtaining samples being inactiveto take a successive sample until a delay time has elapsed sincedisinfectant was injected into the pool.
 3. Apparatus for controllingdisinfectant concentration as set forth in claim 2 wherein said secondmeans for injecting includes a peristaltic pump controlled by said meansfor measuring.
 4. Apparatus for controlling disinfectant concentrationas in claim 2 wherein said means for repetitively obtaining samplesreceives said samples from a location wherein the disinfectantconcentration is the lowest.
 5. Apparatus for controlling disinfectantconcentration as in claim 2 wherein said means for repetitivelyobtaining samplings includes means for flushing said means for receivingprior to each successive sample.
 6. Apparatus for controllingdisinfectant concentration as in claim 2 wherein said first meansincludes a fixed volume chamber, first valve means for supplying saidchamber with said indicator and for retaining said indicator in saidchamber, and second valve means for admitting said indicator from saidchamber into said means for receiving.
 7. Apparatus for controllingdisinfectant concentration as in claim 2 further comprising means foractuating said means for measuring for a predetermined time intervalduring each repetitive sampling.
 8. Apparatus for controllingdisinfectant concentration as set forth in claim 2 further comprisingmeans for discharging the measured amounts of sampled water andindicator to waste and not to the pool after measuring the disinfectantconcentration.
 9. Apparatus for controlling disinfectant concentrationas set forth in claim 2 wherein said receiving means includes a stirrerand electromagnetic means for vibrating said stirrer to mix the waterwith the indicator prior to measuring.